KR100849036B1 - The comparator which has a variable hysteresis - Google Patents

Abstract

The present invention relates to a comparator with variable hysteresis, the object of which is to add a current variable circuit that allows additional current to flow in parallel to the drain and source of the MOSFET, which serves as positive feedback. By adjusting the threshold voltage of the hysteresis, an output voltage is not affected by a small change in the input voltage, but a comparator having a variable hysteresis is provided so that the output voltage is reversed when the input voltage fluctuates above a certain threshold voltage value.

The present invention for achieving the above object is connected to the power supply voltage (VDD) and the M1, M2 MOS transistor for receiving an input signal to the gate, the drain is connected to the M1, M2 MOS transistor and drain and the power supply voltage ( VDD) is composed of M3 and M4 MOS transistors to receive the gate, and the comparator 100 for comparing the reference voltage and the input signal and outputting a signal, and the drain is connected to the drain of the M2 MOS transistor of the comparator. The gate is composed of an M6 MOS transistor connected to the gate of the M3 MOS transistor, and an M7 MOS transistor connected to the drain of the M1 MOS transistor of the comparator of the drain, and the gate is composed of an M7 MOS transistor connected to the gate of the M4 MOS transistor. Variable according to the output signal of the comparator so that it has a positive threshold voltage and a negative threshold voltage In the hysteresis comparator consisting of a positive feedback unit 200, the comparator having a variable hysteresis characterized in that it comprises a variable unit 300 is connected in parallel with the positive feedback unit 200 to adjust the current The technical point is about.

Comparator, Hysteresis, Variable, Threshold, Morse Transistor

Description

The comparator which has a variable hysteresis

1 is a circuit diagram according to an embodiment of a comparator having variable hysteresis according to the present invention;

2 is a circuit diagram showing in detail a variable part according to an embodiment of a comparator having variable hysteresis according to the present invention;

3 is a circuit diagram illustrating a current flow of a variable part according to an embodiment of a comparator having variable hysteresis according to the present invention;

4 is an input / output graph showing a change in hysteresis according to a current change of a comparator having variable hysteresis according to the present invention;

5 is an experimental graph when 0,0 bits are input to a digital inverter of a comparator having variable hysteresis according to the present invention;

6 is an experimental graph when 0,1 bits are input to a digital inverter of a comparator having variable hysteresis according to the present invention;

7 is an experimental graph when a bit of 1,0 is input to a digital inverter of a comparator having variable hysteresis according to the present invention;

8 is an experimental graph when 1,1 bits are input to a digital inverter of a comparator having variable hysteresis according to the present invention;

Explanation of symbols on the main parts of the drawings

100: comparator 200: positive feedback unit

300: variable unit 310: digital inversion circuit

311: first inversion circuit 312: second inversion circuit

320: current variable circuit 321: first variable circuit

322: second variable circuit 323: third variable circuit

324: fourth variable circuit

The present invention relates to a comparator with variable hysteresis, and more particularly to a current variable circuit that allows additional current to flow in parallel to a drain and a source of a MOSFET serving as positive feedback. In addition, by adjusting the hysteresis threshold voltage, the output voltage is not affected by a slight change in the input voltage, but the comparator having a variable hysteresis causes the output voltage to be reversed when the input voltage fluctuates above a certain threshold voltage value.

Typically, the comparator compares the input voltage with the reference voltage and amplifies the difference to output a 'high' or 'low'.

Conventional comparators do not have a noise compensation function at the output, so a separate analog or digital compensation circuit is added.

As a circuit to solve the noise problem, a Schmitt Trigger circuit having hysteresis characteristics has been added to the comparator. In determining the voltage and voltage, Vth-) has a disadvantage of being sensitive to process changes.

Therefore, these days, the comparator itself is designed to have hysteresis specificity.

A comparator with hysteresis has no change in output if the input voltage decreases while the output maintains high at the '0' point. If it continues to decrease and the input voltage reaches the lower reference voltage, the output will fall from 'high' to 'low'.

In that state, when the input voltage increases, it keeps 'low', but when the upper reference voltage is reached, it transitions from 'low' to 'high'. The hysteresis characteristic refers to two points where the output voltage changes, that is, the upper reference voltage and the lower reference voltage.

Since the hysteresis characteristics are implemented to implement a comparator that is resistant to noise, when the hysteresis characteristics vary depending on the process, an error occurs in the comparator itself, which causes a problem in the reliability of the entire semiconductor operation.

On the other hand, when the size of the input signal is changed or the noise is too high, or the size of the input signal is not constant, and the threshold voltage can not be adjusted when switching to various standards or various signal methods, There was a difficulty in using a comparator with a threshold voltage.

The present invention was created in order to solve such a conventional problem, and the variable to allow additional current to flow in parallel to the drain and source of the MOSFET (MOSFET) that serves as a positive feedback By installing a circuit, the threshold voltage can be changed by adjusting the ratio of current flowing through the transistor, so that the hysteresis can be changed even when the size of the input signal is varied, the input signal is varied, or the noise is high. It is an object of the present invention to provide a comparator with variable hysteresis which makes it possible to use a comparator suitable for the present invention.

The comparator of the present invention for achieving the above object is a comparison unit for outputting a signal by comparing the reference voltage and the input signal, and the output signal of the comparison unit so that the output signal of the comparison unit has a positive threshold voltage and a negative threshold voltage A positive feedback unit which is variable according to the present invention is characterized in that it is composed of a variable unit for adjusting the current of the positive feedback unit.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram according to an embodiment of a comparator having variable hysteresis according to the present invention, and FIG. 2 is a circuit diagram specifically showing a variable part according to an embodiment of a comparator having variable hysteresis according to the present invention.

According to the present invention, the comparator compares the reference voltage and the input signal and outputs a signal, and the comparator according to the output signal of the comparator such that the output signal of the comparator has a positive threshold voltage and a negative threshold voltage. The variable positive feedback unit 200 and the variable unit 300 to adjust the current of the positive feedback unit are configured.

The comparator 100 is connected to a power supply voltage VDD and includes an M5 MOS transistor for flowing a constant current, an M1 and M2 MOS transistor for receiving an input signal through a gate, and a drain of the M1 and M2 MOS transistor. The M3 and M4 MOS transistors are connected to the drains of the gates and receive the power supply voltage VDD through the gates, and are connected to the positive feedback unit 200.

The positive feedback unit 200 has a drain connected to the drain of the M2 MOS transistor of the comparator, a gate of the M6 MOS transistor connected to the gate of the M3 MOS transistor, and a drain connected to the drain of the M1 MOS transistor of the comparator. The gate is composed of an M7 MOS transistor connected to the gate of the M4 MOS transistor.

The variable part 300 is connected in parallel with the M6 and M7 MOS transistors and is composed of a digital inversion circuit 310 and a current variable circuit 320.

The digital inversion circuit 310 may transmit a signal for operating the current variable circuit 320, and the first inversion circuit 311 and the second inversion for supplying or blocking a reference voltage by an input signal. The circuit 312 is comprised.

The first inverting circuit 311 allows one of the P-MOS transistor Mfp and the N-MOS transistor Mfn to conduct according to the signal of the input unit 313 to apply a power supply voltage to the current variable circuit 320. Or block it. That is, the P-MOS transistor Mfp and the N-MOS transistor Mfn are connected in series, and the power supply voltage VDD can be supplied to the P-MOS transistor Mfp, and each gate is connected to the input unit. When the signal from the input unit 313 is 0, the P-MOS transistor Mfp is turned on to supply the reference voltage VDD to the current variable circuit 320. When the signal is 1, the N-MOS transistor Mfn is It is conducted so that voltage supply to the current variable circuit 320 can be cut off, and the second inversion circuit has the same circuit configuration as the first inversion circuit.

The current variable circuit 320 includes a first variable circuit 321 and a second variable circuit 322 connected in parallel with the M6 MOS transistor, and a third variable circuit 323 and a fourth connected in parallel with the M7 MOS transistor. The variable circuit 324 is configured, and the first variable circuit 321 and the third variable circuit 323 operate by input signals of the first inverting circuit 311, and the second variable circuit 322 and the fourth variable. The variable circuit 324 is operated by the input signal of the second inverting circuit 312.

The first variable circuit 321 may include an M8a MOS transistor connected to receive a signal input from the digital inversion circuit 310 at a gate, an M8 MOS transistor having a drain connected to a source of the M8a MOS transistor, and a gate of the first variable circuit 321. The M8b MOS transistor is connected to the gate of the M8 MOS transistor and the drain is connected to the gate of the M8 MOS transistor, and the source is composed of the M8b MOS transistor.

The second variable circuit 322 is the same as the connection configuration of the first variable circuit 321, the third variable circuit 323 and the fourth variable circuit 324 is connected in parallel to the M7 MOS transistor and the first variable The configuration is the same as that of the circuit 321 and the second variable circuit 322.

On the other hand, the current variable circuit 320 may be connected in parallel at least two stages, characterized in that the range that can vary the current is increased as the multiple stages are connected.

In addition, the MOS transistors of the variable current circuits of the current variable circuit 320 are designed differently, but the MOS transistors of the first variable circuit and the fourth variable circuit are the same size, and the second variable circuit and the third variable circuit are designed to be the same. By designing the same size of the MOS transistor of the variable circuit it is characterized in that it is possible to adjust a variety of threshold voltages.

Referring to the operation of the comparator of the present invention configured as described above is as follows.

3 is a circuit diagram illustrating a current flow of a variable part according to an embodiment of a comparator having variable hysteresis according to the present invention, and FIG. 4 is an input / output graph showing a change in hysteresis according to a current change of the comparator having variable hysteresis according to the present invention.

5 is an experimental graph when 0,0 bits are input to the digital inverter of the comparator with variable hysteresis of the present invention, and FIG. 6 is 0,1 bit in the digital inverter of the comparator with variable hysteresis of the present invention. Fig. 7 shows an experimental graph when a bit of 1,0 is input to a digital inverter of a comparator having a variable hysteresis of the present invention, and Fig. 8 shows a digital inverter of a comparator with a variable hysteresis of the present invention. The experimental graph when 1, 1 bit is input to is shown.

First, an input signal is received from the digital inverting circuit 310 so that the current can be changed to change the hysteresis of the comparator 100 of the present invention.

When the input signal of 'low' enters into the first inverting circuit 311 and the second inverting circuit 312, the P-MOS transistor Mfp is turned on and the N-MOS transistor Mfn is blocked. Therefore, the voltage is supplied to the current variable circuit 320 from the input voltage VDD connected to the P-MOS transistor Mfp to give a high signal to all of the MOS transistors so as to conduct the current variable circuit 320. do.

For example, referring to the first variable circuit 321, the M8a MOS transistor and the M8b MOS transistor are conducted by receiving the 'high (1)' signal supplied from the digital inversion circuit 310, and the M8 MOS transistor is connected by the M8b MOS transistor. As the voltage at the gate of the transistor is increased, the M8 MOS transistor becomes conductive, thereby creating a way for the current to flow.

Accordingly, the current ID6 flowing into the MOS transistor M6 of the positive feedback unit 200 flows into the first variable circuit 321 and the second variable circuit 322 and thus flows into the M6 MOS transistor. The current ID6 becomes extremely small so that the threshold voltage hardly appears.

On the other hand, when the signal of the 'low (0)' of the first inverting circuit 311 and the 'high (1)' of the second inverting circuit 312 is input, the first inversion circuit 311 is turned on and the second inversion The circuit 312 is to be cut off. Accordingly, the first variable circuit 321 and the third variable circuit 323 become conductive, and the second variable circuit 322 and the fourth variable circuit 324 are blocked. Accordingly, the current ID6 flowing into the M6 MOS transistor of the positive feedback unit 200 flows into the first variable circuit 321, which is the first inverting circuit 311 and the second inverting circuit 312 described above. In this case, a larger current flows and the threshold voltage becomes larger than when a low signal is applied to all of them.

On the other hand, when the first inverting circuit 311 is a 'high (1)', the second inverting circuit 312 is a 'low (0)' signal when the first inversion circuit 311 is cut off and the second inversion Circuit 312 is made conductive. Accordingly, the second variable circuit 321 and the fourth variable circuit 323 become conductive, and the first variable circuit 322 and the third variable circuit 324 are blocked. Accordingly, the current ID6 flowing into the M6 MOS transistor of the positive feedback unit 200 is divided into the second variable circuit 321, which is the size of the MOS transistor of the first variable circuit 321 described above. Since the MOS transistors of the second variable circuit 322 have different sizes, the current flows larger than when the input signals 0 and 1 are received.

On the other hand, when both the first inverting circuit 311 and the second inverting circuit 312 is input the signal of the 'high (1)' to be blocked by both the first inverting circuit 311 and the second inversion circuit (312) Therefore, the current variable circuit is cut off. Accordingly, there is no change in the current ID6 flowing into the M6 MOS transistor of the positive feedback unit 200, and has the largest threshold voltage.

As described above, the current variable circuit 320 can be turned on and off according to the input signal of the digital inverting circuit 310 so that the input current can be divided and flowed so that the threshold voltage can be adjusted by varying the current. If the signal comes in, it can all be used.

On the other hand, the MOS transistors in the variable circuit for designing different sizes of MOS transistors for the first variable circuit, the second variable circuit, the third variable circuit, and the fourth variable circuit, and receiving the input signal from the first inverting circuit 311. The threshold voltage is different because the magnitude of the MOS transistor in the variable circuit receiving the input signal from the second inverting circuit 312 is different from each other. appear. This is because the MOS transistor of the variable circuit driven by the input bit of the digital inverting circuit 310 is designed differently so that the magnitude of the current flowing through the variable circuit is configured differently so that the threshold voltage when the input signal is 01 and 10 By differentiating the threshold voltage for each input signal different from each other can be conveniently used in a variety of fields and a variety of input signals.

Although the above-described embodiments have been described with respect to the most preferred embodiments of the present invention, it is not limited to the above embodiments, and it will be apparent to those skilled in the art that various modifications can be made without departing from the technical spirit of the present invention.

As described above, according to the comparator of the present invention, a transistor is provided by additionally installing a variable circuit which allows an additional current to flow in parallel to the drain and the source of the MOSFET serving as the positive feedback. The threshold voltage can be changed by adjusting the ratio of the current flowing through it, so the hysteresis can be changed even when the magnitude of the input signal is changed, the input signal is varied, or the noise is severe, so that a comparator suitable for various signal types can be used. It is a very useful invention.

Claims (6)

M1 and M2 MOS transistors connected to a power supply voltage VDD and receiving an input signal through a gate, and drains are connected to drains of the M1 and M2 MOS transistors, and may receive a power supply voltage VDD through a gate. Comparing unit 100 is composed of M3, M4 MOS transistors to compare the reference voltage and the input signal and output a signal, The drain is connected to the drain of the M2 MOS transistor of the comparator, the gate is connected to the gate of the M3 MOS transistor, the drain is connected to the drain of the M1 MOS transistor of the comparator, and the gate is connected to the gate of the M4 MOS transistor. In the hysteresis comparator consisting of a positive feedback unit 200 composed of the M7 MOS transistor connected to the output signal of the comparator is changed according to the output signal of the comparator so that the output signal has a positive threshold voltage and a negative threshold voltage, Comparator having a variable hysteresis, characterized in that it comprises a variable unit 300 is connected in parallel with the positive feedback unit 200 to adjust the current. The method of claim 1, The variable part (300) is connected in parallel with the M6, M7 MOS transistor and comparator having a variable hysteresis, characterized in that consisting of a digital inversion circuit (310) and a current variable circuit (320). The method of claim 2, Comparator having a variable hysteresis, characterized in that the variable unit 300 can be connected in parallel two or more stages. The method of claim 2, The digital inversion circuit 310 may transmit a signal for operating the current variable circuit 320, and the first inversion circuit 311 and the second inversion for supplying or blocking a reference voltage by an input signal. Circuit 312, The first inverting circuit 311 is connected to the P-MOS transistor Mfp and the N-MOS transistor Mfn in series, so that the power supply voltage VDD can be supplied to the P-MOS transistor Mfp. Is connected to the input unit, and when the signal from the input unit 313 is 0, the P-MOS transistor Mfp is turned on to supply the reference voltage VDD to the current variable circuit 320, and when the signal is 1 The N-MOS transistor Mfn is turned on to cut off the supply of voltage to the current variable circuit 320, and the second inversion circuit has the same circuit configuration as that of the first inversion circuit. Having a comparator. The method of claim 2, The current variable circuit 320 includes a first variable circuit 321 and a second variable circuit 322 connected in parallel with the M6 MOS transistor, and a third variable circuit 323 and a fourth connected in parallel with the M7 MOS transistor. The variable circuit 324 is configured, and the first variable circuit 321 and the third variable circuit 323 operate by input signals of the first inverting circuit 311, and the second variable circuit 322 and the fourth variable. Comparator with variable hysteresis, characterized in that the variable circuit (324) is operated by the input signal of the second inverting circuit (312). The method of claim 5, wherein The first variable circuit 321 may include an M8a MOS transistor connected to receive a signal input from the digital inversion circuit 310 at a gate, an M8 MOS transistor having a drain connected to a source of the M8a MOS transistor, and a gate of the first variable circuit 321. An M8b MOS transistor connected to the gate of the M8 MOS transistor, a drain connected to the gate of the M8 MOS transistor, and a source connected to the gate of the M6 MOS transistor, The second variable circuit 322 is the same as the connection configuration of the first variable circuit 321, but has a different size than the Morse transistor beam of the first variable circuit 321, The third variable circuit 323 and the fourth variable circuit 324 are connected in parallel to the M7 MOS transistor, the third variable circuit 323 is the first variable circuit 321, the fourth variable circuit 324 is Comparator having variable hysteresis, characterized in that the connection configuration of the second variable circuit (322) and the size of the internal transistor are the same.

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